RU2286520C1 - Method of drying thermolabile dispersed materials - Google Patents

Abstract

FIELD: drying solid materials.

SUBSTANCE: method comprises vibrating dehydration of thermolabile dispersed materials in the fluidized bed by means of alternative heating and cooling in specified time intervals. In the intermediate stages of cooling, the dried cooled air is used, whereas in the final stage, the material is dried up to a given humidity by means of cold air in the loosened condition.

EFFECT: enhanced efficiency and environmental protection.

1 dwg

Description

The claimed invention relates to a technology for drying thermolabile materials and can be used in the microbiological, food, chemical and pharmaceutical industries.

The closest in technical essence and the achieved effect is oscillatory dehydration of thermolabile materials in a suspended layer. In the known drying method (adopted as a prototype), the fluidized-bed drying process under an oscillating mode — alternately heating and cooling the material at certain intervals — is carried out using hot and cold air that is taken from the environment [I. Lyuboshits, Slobodkin L.S., Pikus I.F. Drying of dispersed heat-sensitive materials. - Minsk .: Science and technology, 1969. - P.54, 160-189].

Its humidity is quite high and can be approximately 85%. As a result, the drying time is significantly increased. The final stage of drying, like the previous ones, is also carried out in a fluidized bed. Therefore, as drying material with low mechanical strength (for example, granules of baking yeast) is partially crushed due to the contact of the granules with each other and with the walls of the drying chamber [Shishatsky Yu.I. Drying baking yeast. - Voronezh: Ed. Voronezh. University, 1992. - S.33-37].

The pulverized material after its isolation in cyclones is returned to production, mixed with the starting material and dried again. As a result, the quality of the finished product is reduced. Together with the exhaust air, part of the pulverized material is released into the atmosphere, polluting the environment.

An object of the invention is the intensification of the drying process, improving the quality of the finished product, reducing energy consumption for drying, as well as reducing environmental pollution.

The technical problem is achieved by the fact that in the drying method, which includes oscillating dehydration of thermolabile dispersed materials in a fluidized bed — alternating heating and cooling at certain intervals, according to the invention, dried cold air is used in the intermediate cooling stages, and at the final stage, drying to a predetermined final humidity is carried out in a loosened layer with cold air. Due to the use of dried cold air at the stages of intermediate cooling, drying is significantly accelerated, since the difference in the partial pressure of water vapor above the surface of the material and in the environment increases. The humidity of the dried cold air at the first cooling stage is 0.5%, at the last - 5%, which, together with the short duration of each cooling stage (5-10 s), eliminates the drying of the surface of the material and, consequently, a decrease in its quality. At the final stage, when the moisture content of the material is reduced from 10-15% to 6-8% due to drying in the loosened layer with cold air, the mechanical abrasion of the material is significantly reduced, its overheating does not occur and the quality of the finished product improves. In addition, the concentration of pulverized material in the exhaust air is reduced.

The implementation of the proposed method is illustrated using the dryer shown in the drawing. The dryer is a rectangular apparatus, divided by vertical partitions 2 into a number of chambers 1 so that in some there is a process of heating with hot air passing through the heaters 7, and in others - the cooling process with dried air passing through the dehumidifiers 6. The air enters through the supply ducts 5 under gas distribution grills 3. In the last cooling chamber, blades 4 are installed, the angle of which is adjustable.

The material to be dried passes sequentially through the heating and cooling chambers. Using an oscillating mode allows you to use a coolant with a higher temperature than with the conventional drying method without compromising product quality. In the intermediate cooling chambers, the material is cooled by the self-evaporation of moisture, while the heat accumulated by the particles in the heating chambers is used. The use of dried air for cooling intensifies the process, leads to a quick equalization of humidity along the particle cross section, and the material enters the heating chamber not only with a partially reduced temperature averaged over the volume, but also with an even lower temperature of the surface layer of the particles. In the last chamber, drying to a final specified humidity is carried out in a loosened layer by cold air, which virtually eliminates the abrasion of the material and its overheating, eliminating heat consumption for heating the air. By changing the angle of inclination of the blades in the chamber, the speed of movement of the material is equal to the speed of movement in the previous chambers.

Thus, the proposed method intensifies the drying of thermolabile dispersed materials, improves the quality of the finished product, reduces the energy consumption for drying, and also reduces environmental pollution by a powdery product.

Claims (1)

The drying method, which includes oscillating dehydration of thermolabile dispersed materials in a fluidized bed — alternating heating and cooling at certain intervals, characterized in that dried intermediate air is used in the intermediate cooling stages, and at the final stage, the drying to a predetermined final humidity is carried out in a loosened layer with cold air .